In May, adult Yellowstone cutthroat trout (Salmo clarkii lewisii) moved from Kiakho Lake into its outlet to spawn. Upon emergence from the gravel, most young fry descended at night from the fast flowing, gravel bottom areas into slow flowing, mud and sand bottom regions where they spent the summer. The majority of fry over-wintered in the creek before ascending to the lake. The research was conducted in the summers of 1959 and 1960. It had two objectives: (1) to describe fry distribution and (2) to examine some characteristic fry "behavior" including movement. Traps and an experimental trough were operated. Behavior was observed, movements of marked fish were studied, and fry distribution was determined. Temperature, barometric pressure, water level, and light were recorded. Darkness apparently influenced the downstream movement of recently emerged fry for 90% of it occurred at night. A slow current apparently greatly slowed the rate of descent. The gradual descent of these fry in the "sluggish" Beaver Meadow during July evidently produced the late July uniform Beaver Meadow fry density. Long distance upstream and downstream movement of "healthy" fry in August was quite limited though short temporary movements of fry from their "home", may have been common. At least 60% of the fry held the same "home" for two weeks. Fry defended territories. The August 1960 Beaver Meadow fry population decrease was due to natural mortality. Month-old Beaver Meadow descending fry were characterized by small size and "physical weakness". In a week, the number of day versus night descenders was about equal, but within a 24 hour period, there was no correlation between the two. Bright moonlight appeared to depress night downstream movement, a fluctuating water level may have increased it, and a week long drop in creek temperature apparently depressed all downstream movement. Fry moving upstream were generally larger than average size fry. There was a moderate association between rising daily maximum water temperature over a period of several days and increased upstream movement. Fry in a trough ascended more at 20°C. than at 9°C. A week long drop in water temperature likely depressed movement. Because more than 80% of the movement occurred in the day, a certain minimum light intensity may be required before fry ascend much. The Kiakho outlet observations were compared to the findings of other researchers. Generally, stream dwelling Salmoninae appear to exhibit territorialism, homing, and limited movement,, Several other generalizations about stream dwelling trout, were suggested,, / Science, Faculty of / Zoology, Department of / Graduate

Various aspects of rainbow trout (Salmo gairdneri) predation on migrating sockeye salmon (Oncorhynchus nerka) fry and rainbow trout eggs were studied during 1970-71 in specially-constructed artificial streams, and in the laboratory. Tests involving sockeye fry as prey were conducted near Babine Lake, British Columbia, while those using rainbow trout eggs were done near Abbotsford, British Columbia. Examination of the effects of physical factors such as water velocity, water turbidity, and light intensity on predation on migrating sockeye fry showed mortality to be inversely related to water velocity and water turbidity; inversely related to light intensity at low light levels but directly related at very low levels. Other stream tests showed mortality to be inversely related to the amount of exposure of predators to fry, before the beginning of a nightly fry migration. Exposing predators to abnormal light for varying periods of time, immediately prior to fry migration, reduced over-all mortality during fry migration. Mortality was not proportional to the length of exposure of predators to abnormal light. Fry experience with predators was shown to increase the ability of fry to escape or avoid predation on subsequent predator encounters. Additional experience served to further increase their ability to escape or avoid predators. Conclusions drawn from stream tests and a behavioral study are that experienced fry migrate in a manner rendering them less susceptible to predation and the migration pattern (compact and in mass) is influenced in part, or completely, by encounter and escape from predator-prey interactions experienced earlier. "Handling" or other fright-evoking stimuli appeared to have similar effects. Rainbow trout feeding on colored fish eggs indicated color preference patterns which are influenced by background coloration (color contrast between food and background), and light intensity. Preference was for colors showing the most contrast with the background at a particular light intensity. At low light levels, on a pale-blue background, preference was for lighter colors, while it was for darker colors at high light levels. Mortality differences increased proportionately with contrast between colors. Finally, trout displayed what appears to be a behavioral preference for red, and possibly blue, regardless of surrounding environmental conditions. In a food deprivation study rainbow trout displayed an S-shaped hunger response curve when fed on eggs. Indications were that rainbow trout will feed to gut capacity when given the opportunity. Finally, beyond an upper limit of food deprivation, the amount of food eaten by an individual remains fairly constant. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

No description available.

This study primarily attempts to develop models to estimate population dynamic parameters from mark-recapture data. Model implementation is illustrated using data collected from the South African Pomatomus saltatrix fishery . The models developed allow for the estimation of mortality, survival and migration rates in exploited fish stocks. A growth model is also developed which simultaneously estimates growth parameters as well as validates the hard structure banding using age-length and markrecapture data. There are number of advantages to these models . Given appropriate datasets the mark-recapture models developed in this study can be applied to others species of interest. The models can be modified easily e.g. the growth model can incorporate growth functions other than the von BertalanfIy model. The models can be programmed into a spreadsheet which facilitates the estimation of parameter variances using likelihood profile or bootstrapping methods and allows the testing of model assumptions based on simulations. A general mortality model is developed and is illustrated with mark-recapture data from the P. saltatrix fishery. The model provides an estimate of the average fishing mortality for the Cape and KwaZulu-Natal and is then extended to include movement between the Cape and KwaZulu-Natal. It utilises mark-recapture data from the Sedgwick's-ORI Tagging Programme as well as effort and catch data from the National Marine Linefish System (NMLS). Estimates of annual fishing mortality rates in KwaZulu-Natal are derived from the model which takes into account immigration of P. saltatrix into KwaZulu-Natal from the Cape as well as emigration from KwaZulu-Natal to other areas including the Cape. The average fishing mortality rate was estimated to be 0.27 year" between 1984 and 1993 in the Cape and KwaZulu-Natal combined. This is likely to be underestimated because of non-reporting of tags, shedding of tags and tag-induced mortality. The model is shown to be robust for estimating the average fishing mortality rate and exploitation rate only when annual variability in fishing mortality is small during the study period. The second model to quantify migration into and out of KwaZulu-Natal waters suggested that the whole adult Cape stock migrates into KwaZulu-Natal during winter. Further, this whole stock is available to fishing in KwaZulu-Natal although there is probably large exchange between inshore and offshore areas and, in the latter zone, P. saltatrix is inaccessible to shore-based fishing. Large fishing mortality rates for the years 1987 to 1993 were estimated in KwaZulu-Natal. These large fishing mortality rates may prevent the return migration of P. saltatrix to the Cape and the model predicts that possibly less than 4% actually return to the Cape. An age and growth study based on otolith readings was also undertaken. Validation of the growth banding as annual was confirmed by developing a model that estimated growth parameters using age-length data and simultaneously estimating times-at liberty of tagged individuals based on arbitrarily chosen band deposition periodicities. It is shown that the assumption of annual banding led to the best prediction of periods of liberty of tagged individuals with small coefficients of variations in the parameter estimates. However, since only a few tagged animals were used in the analysis more research is needed to verify the robustness of this technique for use on other fish. The growth of P. saltatrix in the present study was found to be faster than that of a previous study in South Africa. A modified delay-difference model was developed to estimate relative biomass and relative catch based on observed mean body weights and effort indices. For the period 1956 to 1972 the model predicts that there was a decline in P. saltatrix abundance with corresponding declines in mean weight of the catch. Although during this period there was a general decline in fishing mortality, the fishing mortality was sufficiently high for growth overfishing to occur. It was found that during the 17 year period there was a 44% reduction in biomass which is similar to an estimate in another study. Catch during the period was annually variable but generally declined with time especially in the later years. The decline in average weight harvested and the variable but lower catches during this period are consistent with observations by fishers . An evaluation of the present closed season for P. saltatrix in conserving egg production was performed. It showed that better conservation of egg production is possible by shifting the present closed season (September to November) to extend over the October to December season but this may adversely affect the tourism industry in KwaZulu-Natal. Shortening the present closed season by one month (September) does not affect egg production but increases present yield levels. This study suggests that the closed season may not be useful in terms of reducing the fishing mortality rate on P. saltatrix as fishers may be encouraged to fish harder in the open season to make up for the lost yields of the closed season. Moreover, lengthy closed seasons may also increase fishing mortality because fishers tend to fish harder in the months open to fishing. Assuming no large annual recruitment variations the P. saltatrix stock is presently optimally exploited as current fishing mortality rates are just below the MSY or optimum yield levels. / Thesis (Ph.D.)-University of Natal, 1996.

Various aspects of downstream migratory behavior of sockeye salmon fry (pncorhynchus nerka) were examined in a series of field and laboratory experiments. The field work at the Department of tie Environment (Fisheries and Marine Service) Fulton Eiver spawning channels, Babine Lake, British Columbia, was concerned with the predation by rainbow trout (Salmo gairdneri) and whitefish (Prosopium williamsoni) on sockeye fry with various kinds of prior experience. The laboratory studies focused on the effects of exposure to light on the behavior of emerging and recently emerged fry. The results showed that : (1) the number of fry moving downstream varies throughout the nightly migration period; (2) the presence cf predators modifies the movement pattern of migrating fry, such that the fry tend to move downstream over a more concentrated time period; (3) fry response to predators tends not to be predator-specific, migrating fry respond similarly to different species of predators; (4) emergent fry are not all similar in their migratory behavior, some tend to migrate rapidly (fast migrants), while others migrate at a slower rate (slow migrants); (5) generally fry with prior experience to predators displayed different migratory behavior compared to fast and slow migrants; and (6) subjecting newly-emerged fry to increasing time periods of light treatment and fry densities, alters behavior patterns. It is concluded that fry commencing downstream movement are not all similar in their migratory behavior. Begardless of the basis for the behavioral difference between fast and slow migrants, the presence of predators modifies and enhances downstream movement. Further, subjecting premigratory fry to light, alters downstream movement and behavioral interactions between fry. / Science, Faculty of / Zoology, Department of / Unknown

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2007. / Includes bibliographical references (p. 188-204). / Geochemical signatures in the otoliths of diadromous fishes may allow for retrospective analyses of natal origins. In an assessment of river-specific signatures in American shad (Alosa sapidissima), an anadromous clupeid native to the Atlantic coast of North America, stable isotope and elemental ratios in otoliths of juvenile American shad produced accurate natal tags from 12 rivers. Significant inter-annual variability in geochemical signatures from several rivers was detected, due largely to differences in 8180 values among years. The database was further expanded to include 20 rivers from Florida to Quebec, encompassing all major spawning populations. This task was accomplished by collecting juvenile otoliths along with water samples from rivers where juveniles were not sampled. Regressions between otolith and water chemistry for those rivers where both were collected showed significant relationships for Sr:Ca, Ba:Ca, 86180, and 87Sr:86Sr ratios but not for Mg:Ca or Mn:Ca. Despite reducing the combined signature to only four chemical ratios, cross-validated classification accuracies of known-origin juveniles averaged 93%. Ground-truthed signatures were used to classify migrants of unknown origins. Adults returning to spawn in the York River were classified according to their otolith composition. / (cont.) Only 6% of spawners originated from rivers other than the York, supporting the hypothesis that most American shad spawn in their natal river. Of remaining spawners, 79% originated from the Mattaponi River and 21% from the Pamunkey River. The results suggested that while most American shad home to their natal river there is less fidelity to individual tributaries, allowing subsidies to subpopulations with persistent recruitment failure. Otolith signatures were also used in mixed-stock analyses of immature migrants along the coast of Maine in the spring and Minas Basin in the summer. Mixed-stock compositions showed remarkably low diversity and were dominated by fish from the Shubenacadie and Hudson rivers, with an increasing proportion of Potomac River fish over time. In contrast to results from adult tagging studies, southern stocks were virtually absent. These data suggest ontogenetic shifts in migratory behavior. The thesis concludes with a report that water contributed 83% of Sr and 98% of Ba in the otoliths of a marine fish. / by Benjamin Walther. / Ph.D.

No description available.

No description available.

Thesis: Ph. D., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 138-154). / Highly migratory marine fishes support valuable commercial fisheries worldwide. Yet, many target species have proven difficult to study due to long-distance migrations and regular deep diving. Despite the dominance of oceanographic features, such as fronts and eddies, in the open ocean, the biophysical interactions occurring at the oceanic (sub)mesoscale (< 100 km) remain poorly understood. This leads to a paucity of knowledge on oceanographic associations of pelagic fishes and hinders management efforts. With ever-improving oceanographic datasets and modeling outputs, we can leverage these tools both to derive better estimates of animal movements and to quantify fish-environment interactions. In this thesis, I developed analytical tools to characterize the biophysical interactions influencing animal behavior and species' ecology in the open ocean. A novel, observation-based likelihood framework was combined with a Bayesian state-space model to improve geolocation estimates for archival-tagged fishes using oceanographic profile data. Using this approach, I constructed track estimates for a large basking shark tag dataset using a high-resolution oceanographic model and discovered a wide range of movement strategies. I also applied this modeling approach to track archival-tagged swordfish, which revealed affinity for thermal front and eddy habitats throughout the North Atlantic that was further corroborated by synthesizing these results with a fisheries-dependent conventional tag dataset. An additive modeling approach applied to longline catch-per-unit effort data further highlighted the biophysical interactions that characterize variability in swordfish catch. In the final chapter, I designed a synergistic analysis of high-resolution, 3D shark movements and satellite observations to quantify the influence of mesoscale oceanography on blue shark movements and behavior. This work demonstrated the importance of eddies in structuring the pelagic ocean by influencing the movements of an apex predator and governing the connectivity between deep scattering layer communities and deep-diving, epipelagic predators. Together, these studies demonstrate the breadth and depth of information that can be garnered through the integration of traditional animal tagging and oceanographic research with cutting-edge analytical approaches and high-resolution oceanographic model and remote sensing datasets, the product of which provides a transformative view of the biophysical interactions occurring in and governing the structure of the pelagic ocean. / by Camrin Donald Braun. / Ph. D.